There are already known systems for the online ordering of spectacle lenses (see Japanese Patent No. 2,982,991, for instance). With this conventional system, a computer is set up on the side where the spectacle lenses are ordered, and a manufacturer-side computer is connected to this order-side computer so as to allow the exchange of information, with this computer executing order receipt processing such as obtaining lens design data on the basis of order information such as a lens prescription transmitted from the order-side computer. The order-side computer and the manufacturer-side computer perform computational processing according to specific input operations, and perform the processing necessary for placing and taking orders for spectacle lenses while exchanging information with each other.
In prescribing spectacle lenses that correct the vision of a patient's eyes, lenses of the same refractive power (diopter) are prescribed when the left and right eyes both have the same visual acuity, so the curvature of the first refractive surface and the second refractive surface is also the same, and the optical performance, such as astigmatism, curvature of field, and distortion, is also the same. If the visual acuity of the left and right eyes is not the same, however, lenses having different refractive power (diopter) will of course be prescribed.
According to Tscherning's ellipse, which Tscherning discovered as a geometric solution for eliminating astigmatism of a spectacle lens, the optimal base curve for eliminating astigmatism (the refractive power of the first refractive surface) varies. Consequently, if the visual acuity differs between the left and right eyes, the base curve of the left and right lenses must also be different according to Tscherning's ellipse.
Therefore, when lenses are designed according to Tscherning's ellipse, if there is a great difference in visual acuity between the left and right eyes as above, the left and right base curves will also be markedly different.
This means that the curved surface shape of the left and right spectacle lenses looks very unbalanced when the spectacles are viewed from the outside. Consequently, although optical performance is good, the appearance is quite poor.
Furthermore, since the curved surface shape is different for each individual lens on the lens manufacturer side, another disadvantage is higher manufacturing costs.
Accordingly, the same base curve is sometimes used within a specific diopter range in order to lower the manufacturing costs. However, lenses manufactured by this method may have a base curve that is not exactly optimal, so a problem is that the optical performance is inevitably inferior.
Naturally, if the base curves are merely made the same on the left and right in order to improve the appearance, optical performance will be markedly deteriorated in some cases. Thus, if emphasis is placed on the optical performance of the lenses, the cost will be higher and there will be cases in which appearance suffers. On the other hand, the problem with improving the appearance is that the optical performance may suffer.
Also, juvenile myopia tends to increase over time up to a certain age, and this is accompanied by changes in the prescription values for the spectacle lenses. Some wearers, however, are physiologically sensitive to changes in prescription values. That is, they experience severe discomfort when they wear lenses manufactured with a new prescription, and in some cases the body itself may be affected. These symptoms may appear even in regular customers, although not pronounced.
Research conducted by the inventors seems to indicate the primary cause of this to be as follows.
When a lens prescription changes, lenses having a curved surface shape and so forth that match this new prescription are newly designed and manufactured for supply to the customer. In this case, it is not uncommon for the newly designed and manufactured lenses that match the new prescription to have optical performance (astigmatism, curvature of field, and distortion) that is different from the optical performance of the old lenses designed to match the old prescription.
It is believed that symptoms such as discomfort will most often appear if this difference in optical performance goes beyond a certain level.
Thus, the difference in optical performance has been a serious problem, one that occurs due to a diopter difference in prescription lenses resulting from differences between the left and right eyes, or to a diopter difference between new and old lenses.
Unfortunately, the physician who gives the prescription and the business placing the order (such as an optician) do not have access to information about lens design, which has made it difficult to solve this problem.
Also, the existing spectacle lens supply systems mentioned above merely involved having the ordering side (such as an optician) specify lenses to a lens manufacturer, who then supplied the lenses, and no function was in place for solving the above-mentioned problem.
The present invention was conceived in light of the above situation, and it is an object thereof to provide a spectacle lens manufacturing method and a spectacle lens supply method with which good optical performance and good appearance can be both be achieved.